The objective of this proposal is to study the biological function of glucose transporters in the parasite Leishmania mexicana. Leishmania species cause disease in an estimated 12 million individuals worldwide and are a major public health problem. Identification of genes and proteins that serve essential functions for the parasite is critical for the identification of targets for development of novel drugs. Previous work has demonstrated that the glucose transporters of L. mexicana, integral membrane proteins that mediate the uptake of glucose and related hexose sugars, are essential in the amastigote stage of the life cycle that infects vertebrates and causes disease. Hence, this proposal will focus upon the biochemical functions of parasite glucose transporters and attempt to explain why they are essential for the disease causing stage of the parasite life cycle. The first aim will examine each of the 3 principal fates of glucose in the cell and determine which of them is/are impaired by when glucose transporters are genetically ablated by targeted gene deletion. These fates of glucose include: i) incorporation into glycoconjugates and complex carbohydrates, ii) metabolism via the pentose phosphate pathway to generate NADPH and ribose phosphate, and iii) metabolism via glycolysis. These experiments will establish which of these 3 pathways are affected by the inability of a glucose transporter null mutant to import hexoses and which of these deficiencies may contribute to the non-viability of this null mutant as amastigotes. The second aim will investigate the specific functions of the 3 glucose transporter isoforms GT1, GT2, and GT3. Null mutants in each of these genes will be prepared and their phenotypes assessed in both the promastigote and amastigote stages of the life cycle. These experiments will help elucidate distinct functions for each of the 3 glucose transporters expressed by this parasite. Overall, this proposal will provide a detailed biochemical and genetic dissection of glucose transporter function and the essential role of these permeases in the parasite life cycle.